The invention relates to a device with a nozzle beam for producing liquid streams for stream braiding of fibers of a textile web advanced diagonally to the nozzle beam by means of a liquid-permeable substrate, such as a fiber web, consisting of an upper part extending over the working width of the fiber web and a lower part fastened thereto that is liquid-tight, with a pressure chamber being located in the upper part over its length, said chamber being supplied endwise for example with liquid under pressure and with a nozzle sheet attached to the lower part in a liquid-tight manner with holes for the nozzles.
A device of this kind is known from U.S. Pat. No. 4,069,563. The nozzle sheet must be provided with holes arranged quite close together so that a sufficient compaction of the fiber web can be achieved by the plurality of nozzle streams per unit length. Since the number of nozzle openings per centimeter is subject to a limit for reasons of the strength of the nozzle sheet, it is proposed In the US patent to provide the nozzle openings in two rows in the nozzle sheet of the nozzle beam and then to locate the holes with gaps between them, possibly also in three rows in succession, offset relative to one another. This measure produces a high density of nozzle streams side by side. Nevertheless, even with this arrangement and the use of the nozzle beam, characteristic linear stripes visible to the naked eye form in the surface of the compacted fiber web.
U.S. Pat. No. 3,493,462 is significant in this connection. In that patent, a plurality of nozzle beams of this kind are mounted transversely above an endless belt in a frame which can be caused to oscillate and vibrate by means of a device in one corner of the frame. The frequency is intended to be 200-300 movements per minute, in other words 2-5 Hz, and the substrate for the fiber web consists either of a piece of sheet metal, pierced with fine holes, or a fabric with high permeability. The document teaches two methods for embossing the surface on the basis of a number of test conditions:
1. With a stationary nozzle beam, a desired linear embossing is produced by the embossing effect of the nozzle streams.
2. With the nozzle beam moving back and forth, a desired embossing with a curved or zigzag shape is produced. The shape of the curves on the fleece depends on the frequency of the oscillating movements, but only one frequency with a maximum of 5 Hz is provided. Nothing whenever is said about the amplitude of the movements. The embossing produced in this fashion is said to be softer while the surface achieved is smoother.
EP 0 132 128 B1 can also be mentioned in this regard. In that document, a frame with a plurality of nozzle beams located side by side is also disclosed which likewise is intended to be caused to perform an oscillating movement as a whole. In contrast to the US patent, a fleece with a surface that is embossed as it rests on the substrate is to be produced, which therefore shows the negative image of the substrate used. The operating conditions for this purpose are likewise an oscillating frequency of 75 to 200 movements, in other words 1-3.3 Hz with an amplitude of 5-50 mm. In one example, with a forward speed of the fleece of 10 meters per minute, a frequency of 2 Hz and an amplitude of 37 mm are selected. With these values, the fleece is embossed with the structure of the substrate but nothing is said about the surface design on the side which the nozzle streams strike.